1. Field of the Invention
The invention relates to a sun-shade device, more particularly to a sun-shade device which includes a stretching arm unit with upper and lower arm members that are aligned with each other when a screen thereof is fully stretched.
2. Description of the Related Art
A sun-shade device is commonly installed in an automobile adjacent to a rear window for shading the interior of the automobile from sunlight. FIGS. 1 and 2 show a conventional sun-shade device 1 which includes an elongate housing 11 secured in the automobile, an elongate roller 12 journalled in the housing 11, a screen 13 wound on the roller 12 and having an upper edge which extends out of the housing 11 and which is provided with an elongate frame member 15, a torsion spring 14 provided in the housing 11 for biasing the roller 12 to rotate in a direction for winding the screen 13 on the roller 12, a pair of stretching arms 16 mounted on two opposite ends of the housing 14 for stretching the screen 13 out of the housing 14, and a drive unit 17 for driving movement of the stretching arms 16. The frame member 15 on the upper edge of the screen 13 is formed with a longitudinally extending slide groove 151 that opens downwardly. Each of the stretching arms 16 has a lower end portion mounted pivotally on the housing 14 and an upper end portion formed with a sliding block 161 which extends into and which is slidable along the slide groove 151. The drive unit 17 includes a gear member 171 which can be driven by a motor (not shown) and which engages a pair of transmission shafts 18 that are connected respectively and pivotally to the lower end portions of the stretching arms 16. When the motor is activated to drive rotation of the gear member 171, the stretching arms 16 are moved by the transmission shafts 18 to pivot upwardly and downwardly relative to the housing 14 for winding and unwinding the screen 13. However, it is noted that the stretching arms 16 are designed to be inclined relative to a vertical line and to extend toward a central part of the screen 13 when the screen 13 is fully stretched so as to permit smooth operation of the stretching arms 16 when the drive unit 17 is subsequently activated for winding the screen 13. The conventional sun-shade device is thus not satisfactory.